The pre-TCR signal induces transcriptional silencing of the TCRγ locus by reducing the recruitment of STAT5 and Runx to transcriptional enhancers
The pre-TCR signal induces transcriptional silencing of the TCRγ locus by reducing the recruitment of STAT5 and Runx to transcriptional enhancers
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DOI：
10.1093/intimm/dxr055
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发表时间：
2011-09-01
影响因子：
4.4
通讯作者：
Ikuta, Koichi
中科院分区：
文献类型：
--
作者：
Tani-ichi, Shizue;Satake, Masanobu;Ikuta, Koichi
小鼠TCR γ基因座受转录因子STAT 5和Runx的正调控。虽然该基因座在T淋巴细胞中经历频繁重排，但TCR γ转录在α β T细胞中受到抑制。这种现象称为TCR γ沉默，依赖于前TCR诱导的胸腺细胞增殖。然而，TCR γ沉默的分子基础在很大程度上是未知的。在这里，我们表明，前TCR信号减少转录和组蛋白乙酰化的TCR γ基因座的V-J重排无关。我们还证明Runx主要在CD 4（-）CD 8（-）双阴性阶段被募集到TCR γ基因座的E γ和HsA增强子元件，并且Runx与这些元件的结合在胸腺细胞发育的后期阶段减少。重要的是，抗CD 3抗体处理降低了IL-7 R表达水平、STAT 5磷酸化以及STAT 5和Runx向RAG 2缺陷型胸腺细胞中的E γ和HsA元件的募集，表明前TCR信号传导触发了STAT 5和Runx与增强子元件的结合减少。此外，我们观察到在CD 4（+）CD 8（+）双阳性细胞系DPK中错误表达STAT 5或Runx诱导TCR γ基因转录。最后，我们表明，在Runx 3转基因小鼠的α β T细胞中诱导TCR γ转录，表明Runx 3在体内抵消α β T细胞中的TCR γ沉默。我们的结果表明，前TCR信号通过减少STAT 5和Runx的募集间接地使TCR γ增强子失活，并且暗示这种作用是α β T细胞中TCR γ沉默的重要步骤。
The mouse TCR gamma locus is positively regulated by the transcription factors STAT5 and Runx. While the locus undergoes frequent rearrangements in T lymphocytes, TCR gamma transcription is repressed in alpha beta T cells. This phenomenon, known as TCR gamma silencing, depends on pre-TCR-induced thymocyte proliferation. The molecular basis for TCR gamma silencing, however, is largely unknown. Here, we show that pre-TCR signaling reduces transcription and histone acetylation of the TCR gamma locus irrespective of V-J rearrangements. We also demonstrate that Runx is recruited to E gamma and HsA enhancer elements of the TCR gamma locus, primarily at the CD4(-)CD8(-) double-negative stage and that Runx binding to these elements decreases at later stages of thymocyte development. Importantly, anti-CD3 antibody treatment decreased IL-7R expression levels, STAT5 phosphorylation and recruitment of STAT5 and Runx to E gamma and HsA elements in RAG2-deficient thymocytes, suggesting that pre-TCR signaling triggers reduced binding of STAT5 and Runx to the enhancer elements. Furthermore, we observed that misexpression of STAT5 or Runx in the CD4(+)CD8(+) double-positive cell line DPK induces TCR gamma gene transcription. Finally, we showed that TCR gamma transcription is induced in alpha beta T cells from Runx3 transgenic mice, suggesting that Runx3 counteracts TCR gamma silencing in alpha beta T cells in vivo. Our results suggest that pre-TCR signaling indirectly inactivates TCR gamma enhancers by reducing recruitment of STAT5 and Runx and imply that this effect is an important step for TCR gamma silencing in alpha beta T cells.